A single-lens reflex digital camera that is able to convert the optical image of a subject into an electrical image signal and output the signal has been rapidly growing in popularity in recent years. With this single-lens reflex digital camera, the light (or the image of the subject) incident on a camera lens is reflected by a reflecting mirror that is arranged on the photographing optical path behind the lens, and therefore changing the optical path, and is erected into an erect image by passing through a pentaprism and the like, and guided to the optical viewfinder. As a result, a user is able to see the image of the subject that passed through the lenses from the optical viewfinder, when a user and the like observes a subject using a viewfinder. Therefore, the position that the viewfinder optical path is formed is normally the fixed position of the reflecting mirror.
Meanwhile, in the case that the lenses are used for photographing, the reflecting mirror quickly changes the position thereof to retract from the photographing optical path, and by doing so, the viewfinder optical path can be switched to the photographing optical path. Then, the reflecting mirror quickly returns to the fixed position after photographing ends. This system is the same for a conventional silver halide camera or a digital camera, if it is a single-lens reflex system.
One characteristic of a digital camera is that a user takes a picture while looking at a display device (for example, a liquid crystal display monitor used for displaying an image) when photographing, and the image that is photographed can be confirmed immediately after it is taken. However, a problem occurs that a user will not be able to use a liquid crystal display monitor that is used for displaying an image when photographing, if the conventional method of the single-lens reflex reflecting mirror is used in a digital camera. In this way, it becomes extremely difficult especially for a beginner who is inexperienced with photographing using a digital camera to use the camera, because a user is not able to use the liquid crystal display monitor that is used for displaying an image to photograph and can't help photographing by peeping at the viewfinder. Therefore, users demand for a function in the digital camera so that a picture can be taken using a liquid crystal display monitor used for displaying an image even during the time of photographing, and a single-lens reflex digital camera that includes a function in which a picture can be taken using a display device such as a liquid crystal display monitor and the like that is used for displaying an image even during the time of photographing has been proposed (for example, Patent Citation 1).    Patent Citation 1: Patent 2001-125173